1. Field of the Invention
The invention relates to a method for manufacturing a liquid crystal display element, including: providing a long sheet material including a laminate of an optical film containing a polarizer, a pressure-sensitive adhesive layer, and a carrier film temporarily bonded to the pressure-sensitive adhesive layer; cutting the long sheet material at predetermined intervals, while maintaining the continuity of the carrier film; and then continuously bonding the resulting optical film pieces to liquid crystal panels, respectively, while peeling off the carrier film from the optical film pieces.
2. Description of the Related Art
Polarizing plates are essential for liquid crystal display devices. In many cases, polarizing plates are each transported and bonded in the form of a completely cut piece. In such cases, however, there are some problems such as low productivity and a shift in the position of the polarizing plate due to curling of the polarizing plate during a bonding process. Therefore, continuous bonding techniques are proposed (see for example Japanese Patent Application Laid-Open No. 2005-037416 and No. 57-52017).
The continuous bonding process includes unwinding and feeding a polarizing plate from a material roll, performing half cutting in which a laminated structure including the polarizing plate is partially cut in the thickness direction, while part (carrier film) of the laminated structure is left uncut, so that polarizing plate pieces are obtained, and then bonding each piece. The portion left uncut in the half cutting process maintains the continuity and therefore can be used as a carrier, so that cut pieces of the polarizing plate can be continuously bonded to liquid crystal panels, respectively, after the cut pieces of the polarizing plate are transported by a tensile force.
In the half cutting process, however, a pressure-sensitive adhesive layer is sometimes incompletely cut and partially left uncut, depending on the accuracy of the cut depth. When the pressure-sensitive adhesive layer is left uncut in such a manner, the uncut portion of the pressure-sensitive adhesive layer may be torn in the process of peeling off an optical film from a carrier film, so that permanent deformation may occur in which an end portion of the pressure-sensitive adhesive is deformed into a ball shape due to stretching followed by tearing. Particularly when a pressure-sensitive adhesive having low elastic modulus (soft) is used, such deformation of the pressure-sensitive adhesive layer is more likely to occur. In the process from the half cutting to the bonding, the end face cannot be processed, because the polarizing plate is placed on the carrier film. As a result, voids are formed in the liquid crystal panel having the bonded polarizing plate (namely, liquid crystal display element) due to the deformation of the pressure-sensitive adhesive layer, or peeling occurs from the end portion, which may also be a cause of leakage of light from such portions or any other fatal defect.
In order to avoid such problems, the pressure-sensitive adhesive layer may be completely cut in such a manner that the depth of the cut formed by half cutting can reach the carrier film layer. If the pressure-sensitive adhesive layer is completely cut, the pressure-sensitive adhesive layer can be prevented from being deformed in the process of peeling off the optical film piece from the carrier film (see Japanese Patent Application Laid-Open No. 2005-037416).    Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2005-037416    Patent Document 2: Japanese Patent Application Laid-Open (JP-A) No. 57-52017